6 research outputs found
Temperature-dependent energy levels of electrons on liquid helium
We present measurements of the resonant microwave absorption by the Rydberg
energy levels of surface state electrons on the surface of superfluid liquid
helium, in the frequency range 165 - 220 GHz. The resonant frequency was
strongly temperature dependent from 0.1 to 2 K. The experiments are in
agreement with recent theoretical calculations of the renormalisation of the
electron energy levels due to zero-point and thermal ripplons, analogous to a
condensed matter Lamb shift. The temperature-dependent contribution to the
linewidth for excitation to the first excited state at 189.6 GHz is compared
with other measurements and theoretical predictions.Comment: 24 pages, 9 figure
Spin-Polarization in Magneto-Optical Conductivity of Dirac Electrons
A mechanism is proposed based on the Kubo formula to generate a
spin-polarized magneto-optical current of Dirac electrons in solids which have
strong spin-orbit interactions such as bismuth. The ac current response
functions are calculated in the isotropic Wolff model under an external
magnetic field, and the selection rules for Dirac electrons are obtained. By
using the circularly polarized light and tuning its frequency, one can excite
electrons concentrated in the spin-polarized lowest Landau level when the
chemical potential locates in the band gap, so that spin-polarization in the
magneto-optical current can be achieved.Comment: 4 pages, 3 figure